Complex Update Sql Statement

Question

I have two tables one table has an id and a username the name of the table is user . I have another table called value that table has an id which is to store the id from the user table. The table value also has a column called value and item_id which is used to store the item.

I want to write an update statement that updates the following columns within value id, value, item_id however the values I have to execute the statement is username = $username, value = $value and item_id=$item_id (based on the application)

How can I write an update statement that stores the id (username id), value and item_id

The reason for using an update statement is because that user can change the value within the value column at any time

Answer 1

UPDATE `value` SET `value` = $value WHERE item_id = $item_id 
AND user_id IN (SELECT id FROM `users` WHERE username = $username)

be sure to sanitize your database inputs.

this will only update, if you want to create the entry (i assume that user_id and item_id are the combined primary key of your second table), you can use a replace into statement.

please tell me if you need that, because i think it was not the question.

it may be not as efficient but i think that will not really matter, but you can of course fetch the user id first with a separate query.

this will probably be better understandable.

Answer 2

Try this

UPDATE value, user
SET value = $value
WHERE item_id = $item_id
AND value.user_id = user.user_id
AND user.username = $username;